Existence theorems for some elliptic systems.
We study the existence and nonexistence of positive solutions of nonlinear elliptic systems in an annulus with Dirichlet boundary conditions. In particular, a priori bounds are obtained. We also study a general multiple linear eigenvalue problem on a bounded domain.
Nous montrons principalement que, si est une fonction différentiable sur un intervalle , si sa dérivée est höldérienne d’ordre avec et si (resp. quand (resp. alors , qui est absolument continue, admet (presque partout) une dérivée bornée presque partout.
In this paper we discuss the uniqueness of positive solutions of the nonlinear second order system -u'' = g(v), -v'' = f(u) in (-R,R), u(±R) = v(±R) = 0 where f and g satisfy some appropriate conditions. Our result applies, in particular, to g(v) = v, f(u) = u, p > 1, or f(u) = λu + au + ... + au, with p > 1, a > 0 for j = 1, ..., k and 0 ≤ λ < μ where μ = π/4R.
We establish a uniqueness result for an overdetermined boundary value problem. We also raise a new question.
We complement a previous result concerning a converse of the mean-value property for smooth superharmonic functions. The case of harmonic functions was treated by Kuran and an improvement was given by Armitage and Goldstein.
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